Satellite with regenerative processor

ABSTRACT

A satellite system that includes a gateway, a satellite, and a user terminal. The gateway determines a modulation scheme based on a function of uplink and downlink signal quality and a defined relationship between the downlink modulation to the uplink modulation. The satellite includes an input demodulator configured to apply an input modulation and coding (modcod) scheme; an output modulator configured to apply an output modcod scheme; and an output modcod scheme selector configured to select an output modcod scheme for the output modulator based on the input modcod scheme according a predetermined relationship between input modcod schemes and output modcod schemes. The user terminal providing the gateway a measure of downlink signal quality.

BACKGROUND

Wireless communication systems may include a communication platform suchas a dedicated terrestrial antenna, airborne platform, or communicationsspacecraft (e.g., a satellite). Such platforms typically operate withinregulations that allocate at least one operating frequency bandwidth fora particular set of communications. Efficient use of such operatingfrequency bandwidth is a factor in operating a communication system.Adaptive Coding and Modulation (ACM) facilitates efficient use ofbandwidth in various conditions that affect Signal to Noise Ratio (SNR).

In some systems, a satellite may relay data between one or more gatewaysand one or more subscriber terminals. Satellites in such a system maysimply resend a received signal with some amplification and with someshift in frequency. Some satellites also provide some on-boardprocessing of signals. An incoming signal may be demodulated and decodedso that digital content is obtained and may be directed to appropriateoutputs. Outgoing signals are generated from the digital content (e.g.encoded and modulated) in what may be considered a regenerativearrangement. On-board processing generally comes with additional costand complexity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram describing a satellite communication system.

FIGS. 2A-C illustrate aspects of a satellite system.

FIG. 3 illustrates aspects of a regenerative satellite system withdifferent input and output modcod schemes.

FIG. 4 illustrates a satellite with output modcod selection.

FIG. 5 illustrates a satellite with on-board processing.

FIG. 6 illustrates a satellite with switching fabric connecting inputports and output ports.

FIG. 7 illustrates an example of routing of input channels to outputchannels.

FIG. 8 illustrates a switch connected to other switches through ahigh-speed serial link.

FIGS. 9A-C illustrate tables used by an on-board processor.

FIG. 10 illustrates a table linking input and output modcod schemes.

DETAILED DESCRIPTION

A satellite with on-board processing communicates using Adaptive Codingand Modulation (ACM) to adapt to changing conditions. Appropriatemodulation and coding (“modcod”) schemes may be selected forcommunication between the satellite and ground. A first modcod schememay be used for communication between the gateway and the satellite,with a second modcod scheme used for communication between the satelliteand a subscriber terminal. In general, signal-to-noise ratios (SNRs) arelower between a satellite and a subscriber terminal than between agateway and the satellite so that different modcod schemes may beappropriate. The first modcod scheme for gateway-to-satellitecommunication may be selected by the gateway based on SNR feedback fromthe satellite and the subscriber terminal. The second modcod scheme forsatellite-subscriber terminal communication may be determined accordingto the first modcod scheme. First and second modcod schemes may belinked in a lookup table (or in some other way) so that there is apredetermined correspondence between the first modcod scheme and thesecond modcod scheme so that in effect, both are selected together bythe gateway. Thus, the satellite does not need to make a complexdetermination as to which modcod scheme to select based onsatellite-subscriber terminal SNR but simply selects thesatellite-subscriber terminal modcod scheme dictated by thegateway-satellite modcod scheme. Gateway-satellite modcod schemes may belinked to satellite-subscriber terminal modcod schemes according totheir respective encoding rates to ensure outgoing data (e.g. going tosubscriber terminal) can be encoded and sent faster than incoming data(e.g. from gateway) is received and decoded. Thus, buffering of data andhardware associated with buffering may be substantially reduced oreliminated. Neither does the satellite participate in resourceallocation.

A switch in a satellite with on-board processing may directcommunications traffic received by the satellite (e.g. from a gateway)to appropriate outputs, for example, to particular spot beams generatedby the satellite, and in some cases where spot beams have multiplecarriers, to particular carriers of a given spot beam. Assignment ofincoming data (e.g. to spot beams and carriers) may use one or morelookup tables that indicate how to direct incoming data. For example,incoming data received from a gateway may be assigned to multiple outputbeams (e.g. spot beams) in a fan-out arrangement that is determined by atable. Output beams may include multiple carriers and assignment ofincoming data to carriers of different output beams may be indicated bya lookup table. Data may be received in modcod blocks, where a modcodblock is the unit of modulation and encoding of the modcod system (i.e.all data of a modcod block is subject to the same modcod scheme, withchanges in modcod scheme occurring only between modcod blocks). Frameswithin a received modcod block may be distributed to carriers and outputbeams according to a table, or tables. For example, a table may indicatea pattern for distribution of frames of a modcod block to specificcarriers of output beams. This provides a relatively uncomplicated wayto control traffic in the satellite with little or no intervention fromoutside the satellite.

FIG. 1 depicts a block diagram of a wireless communications system thatincludes a communication platform 100, which may be a satellite located,for example, at a geostationary or non-geostationary orbital location.In other embodiments, other platforms may be used such as UAV orballoon, or even a ship for submerged subscribers. In yet anotherembodiment, the subscribers may be air vehicles and the platform may bea ship or a truck where the “uplink” and “downlink” in the followingparagraphs are reversed in geometric relations. Platform 100 may becommunicatively coupled to at least one gateway 105 and a plurality ofsubscriber terminals ST (including subscriber terminals 107). The termsubscriber terminals may be used to refer to a single subscriberterminal or multiple subscriber terminals. A subscriber terminal isadapted for communication with the wireless communication platformincluding as satellite 100. Subscriber terminals may include fixed andmobile subscriber terminals including, but not limited to, a cellulartelephone, wireless handset, a wireless modem, a data transceiver, apaging or position determination receiver, or mobile radio-telephone, ora headend of an isolated local network. A subscriber terminal may behand-held, portable (including vehicle-mounted installations for cars,trucks, boats, trains, planes, etc.) or fixed as desired. A subscriberterminal may be referred to as a wireless communication device, a mobilestation, a mobile wireless unit, a user, a user terminal, a subscriber,or a mobile.

In one embodiment, satellite 100 comprises a bus (i.e. spacecraft) andone or more payloads (i.e. the communication payload). The satellite mayalso include multiple power sources, such as batteries, solar panels,and one or more propulsion systems, for operating the bus and thepayload.

The at least one gateway 105 may be coupled to a network 140 such as,for example, the Internet, terrestrial public switched telephonenetwork, mobile telephone network, or a private server network, etc.Gateway 105 and the satellite (or platform) 100 communicate over afeeder beam 102, which has both a feeder uplink 102 u and a feederdownlink 102 d. In one embodiment, feeder beam 102 is a spot beam toilluminate a region 104 on the Earth's surface (or another surface).Gateway 105 is located in region 104 and communicates with satellite 100via feeder beam 102. Although a single gateway is shown, someimplementations will include many gateways, such as five, ten, or more.One embodiment includes only one gateway. Each gateway may utilize itsown feeder beam, although more than one gateway can be positioned withina feeder beam. Note that the terms “feeder” beams and “service” beamsare used for convenience. Both feeder beams and service beams are spotbeams and the terms are not used in a manner to limit the function ofany beam. In one embodiment, a gateway is located in the same spot beamas sub scriber terminals.

Subscriber terminals ST and satellite 100 communicate over servicebeams; for example, FIG. 1 shows service beams 106, 110, 114 and 118 forilluminating regions 108, 112, 116 and 120, respectively. In manyembodiments, the communication system will include more than fourservice beams (e.g., 60, 100, etc.). Each of the service beams have anuplink (106 u, 110 u, 114 u, 118 u) and a downlink (106 d, 110 d, 114 d,118 d) for communication between subscriber terminals ST and satellite100. Although FIG. 1 only shows two subscriber terminals within eachregion 108, 112, 116 and 120, a typical system may have thousands ofsubscriber terminals within each region.

In one embodiment, communication within the system of FIG. 1 follows anominal roundtrip direction whereby data is received by gateway 105 fromnetwork 140 (e.g., the Internet) and transmitted over the forward path101 to a set of subscriber terminals ST. In one example, communicationover the forward path 101 comprises transmitting the data from gateway105 to satellite 100 via uplink 102 u of feeder beam 102, through afirst signal path on satellite 100, and from satellite 100 to one ormore subscriber terminals ST via downlink 106 d of service beam 106.Although the above example mentions service beam 106, the example couldhave used other service beams.

Data can also be sent from the subscriber terminals ST over the returnpath 103 to gateway 105. In one example, communication over the returnpath comprises transmitting the data from a subscriber terminal (e.g.,subscriber terminal 107 in service beam 106) to satellite 100 via uplink106 u of service beam 106, through a second signal path on satellite100, and from satellite 100 to gateway 105 via downlink 102 d of feederbeam 102. Although the above example uses service beam 106, the examplecould have used any service beam.

FIG. 1 also shows a Network Control Center 130, which includes anantenna and modem for communicating with satellite 100, as well as oneor more processors and data storage units. Network Control Center 130provides commands to control and operate satellite 100. Network ControlCenter 130 may also provide commands to any of the gateways and/orsubscriber terminals.

In one embodiment, communication platform 100 implements the technologydescribed above. In other embodiments, the technology described above isimplemented on a different platform (or different type of satellite) ina different communication system.

The architecture of FIG. 1 is provided by way of example and notlimitation. Embodiments of the disclosed technology may be practicedusing numerous alternative implementations.

In one embodiment, a satellite includes an antenna system that providesa set of beams comprising a beam pattern used to receive wirelesssignals from ground stations and to send wireless signals to groundstations. In one example, an entire service region is covered using onebeam. In another example, however, the antenna system provides a beampattern that includes multiple spot beams, with each spot beam coveringa portion of the service region. The portion of the service regioncovered by a spot beam is referred to as a cell. The individual spotbeams (user beams) divide an overall service region into a number ofcells. For example, U.S. Pat. No. 7,787,819 describes a pattern of 135spot beams covering the continental United States (CONUS), Hawaii,Alaska, and Puerto Rico. It is noted that a service region may bedefined in any manner to cover any desired geographic location. In oneembodiment, the antenna system includes a phased array antenna, a directradiating antenna, or a multi-feed fed reflector.

Dividing the overall service region into a plurality of smaller cellspermits frequency reuse, thereby substantially increasing the bandwidthutilization efficiency. In some examples of frequency reuse, a totalbandwidth allocated to the downlink is divided into separatenon-overlapping blocks for the forward downlink 118 and the returndownlink 115. Similarly, the total bandwidth allocated to the uplink isdivided into separate non-overlapping blocks for the forward uplink 114and the return uplink 119.

In other examples, some or all of the allocated bandwidth for user beamsis reused by the gateway(s) 105, thereby providing for simultaneousoperation of at least a portion of the feeder link and a portion of theuser link at common frequencies. More specifically, forward uplink 102 uand return uplink 118 u may reuse the same frequency and forwarddownlink 118 d and return downlink 102 d may reuse the same frequency.Simultaneous operation of the feeder link 102 and the user link 118 atcommon frequencies means that the gateway(s) 105 may reuse any part ofthe total bandwidth allocated to the user beams. This may beaccomplished in numerous ways known in the art, such as by using spatialisolation, time domain isolation, code isolation, etc.

FIG. 2A depicts a portion of a beam pattern. A cluster of spot beams, oruser beams, is depicted that includes spot beams 142-1-142-16 that areadjacent and at least partially overlapping with at least one other spotbeam in the cluster. The provided example shows a color re-use techniquewith four dedicated color assignments for user beams. The colors maycorrespond to unique combinations of frequency band and antennapolarization d. A small number of spot beams and corresponding coverageareas are shown by way of example, but it will be appreciated that theconcepts may be extended to any number of spot beams or used with fewerspot beams. While an example is described with respect to forwarddownlink signals in user beams from a satellite to subscriber terminals,the concepts are equally applicable to return uplink signals as well.

The spot beams of FIG. 2A are roughly arranged into four rows. A firstrow includes spot beams 142-1, 142-2, 143-2 and 142-4; a second rowincludes spot beams 142-5, 142-6, 142-7 and 142-8; a third row includesspot beams 142-9, 142-10, 1432-11 and 142-12; and a fourth row includesspot beams 142-13, 142-14, 142-15 and 142-16. Each spot beam is assigneda dedicated color, where color is defined as a combination of frequencyband and polarization. The spot beams in the first row alternatededicated downlink color assignments ‘A’ and ‘B,’ beginning with an ‘A’color assignment for spot beam 142-1 and ending with a ‘B’ colorassignment for spot beam 142-4. The spot beams in the second rowalternate dedicated color assignments ‘C’ and ‘D,’ beginning with a ‘C’color assignment for spot beam 142-5 and ending with a ‘D’ colorassignment for spot beam 142-8. The spot beams in the third rowalternate dedicated color assignments ‘A’ and ‘B,’ beginning with an ‘A’color assignment for spot beam 142-9 and ending with a ‘B’ colorassignment for spot beam 142-12. The spot beams in the fourth rowalternate dedicated color assignments ‘C’ and ‘D,’ beginning with a ‘C’color assignment for spot beam 142-13 and ending with a ‘D’ colorassignment for spot beam 142-16. The spot beans 142-1 through 142-16 areanalogous to user/service links 117 of FIG. 1. A uniform pattern, asdepicted in FIG. 2A is not required. Only three subscriber terminals,STs, are illustrated in FIG. 2A. It will be understood that each spotbeam 142-1-142-16 may serve one or more subscriber terminals.

FIG. 2A also depicts a spot beam 150 for communicating with the gateway105. Spot beam 150 is analogous to feeder link 102 of FIG. 1 and can bereferred to as a feeder beam or gateway beam. FIG. 2A shows thatsatellite 100 communicates with gateway 105 in spot beam 150 (also knownas feeder beam 150) using the following colors (frequencyband+polarization): A1, B1, C1, D1, A2, B2, C2, D2, A3, B3, C3, D3, A4,B4, C4, and D4. In this embodiment, the feeder beam 150 uses sixteencolors while each user beam (142-1 to 142-16) uses one color. In oneembodiment, each color of FIG. 2A includes 250 MHz of spectrum andfeeder beam 150 is used to communicate with the subscriber terminals ofuser beams 142-1 to 142-16.

In order to operate a satellite communication system, or other wirelesscommunication system (as the technology described herein is not limitedto satellite communication systems), the operator (or other entity)typically must request permission from an appropriate governmentalauthority to utilize preselected frequency bands. For example, somesatellites are provided with permission to operate in the Ka band, whichincludes uplink frequencies of 28.5-30.0 GHz and downlink frequencies of18.7-20.2 GHz. Other frequency bands can also be used. Higher frequencybands have more capacity (bandwidth) to carry data. Therefore, it isdesirable to operate at higher frequencies. For example, the V band canbe used for uplinks at approximately 50 GHz and the Q band can be usedfor downlinks are approximately 37 GHz. A satellite communication systemmay be allocated up to approximately 5 GHz in each of the V and Q bands.Because the V and Q bands have higher capacity than the Ka band, the Kaband will be referred to as a low capacity frequency band and the Q/Vbands will be referred to as high capacity frequency bands. Other lowcapacity frequency bands also exist (e.g., Ku band, LMDS band, NGSOband). Other high capacity frequency bands also exist (e.g., opticalband, W band and M band). The technology described herein is not limitedto any particular frequency band.

In one embodiment, in order to achieve enough capacity in the feederlinks to have one gateway service subscriber terminals in sixteen (ormore, or fewer) user beams, communication between the satellite will bein high capacity frequency bands such as Q/V bands, while communicationbetween the satellite and the subscriber terminals will be in a lowcapacity frequency band such as Ka band.

FIG. 2B shows an example frequency plan for the feeder beams (such asfeeder beam 150) forward link for one embodiment where communicationbetween the satellite and the gateway will be in high capacity frequencybands such as Q/V bands, while communication between the satellite andthe subscriber terminals will be in a low capacity frequency band suchas Ka band. FIG. 2B shows the colors A1, B1, C1, D1, A2, B2, C2, D2, A3,B3, C3, D3, A4, B4, C4, and D4 in the Q band for the feeder beamdownlinks (return downlink). Right hand circular polarized (RHCP) colorsand left hand circular polarized (LHCP) colors of the same frequency areseparated by the dashed line in FIG. 2B. The frequency plan of FIG. 2Bcan be used for the beam pattern of FIG. 2A.

FIG. 2C illustrates an example of how ACM may be used in a satellitecommunications system. Gateway 105 receives data from a network 140. Thereceived data is encoded and modulated by modulator 160 before beingsent in feeder beam 150. For example, Forward Error Correction (FEC)encoding may be applied using one or more encoding schemes from a rangeof different options (e.g. Low-Density Parity Check (LDCP), turbo code,Bose-Chaudhuri-Hocquenghem (BCI-i) code, or other suitable FEC scheme).For any such scheme, a suitable encoding rate may be selected (i.e. asuitable amount of redundancy). Modulation may use a suitable scheme(e.g. QPSK, 8PSK, 16/32/64/128/256APAK), Modulation and encoding schemes(modcod schemes) for communication with satellites may conform to knownstandards. Examples include the Digital Video Broadcasting (DVB)standards for satellites (DVB-S), DVB-S second generation (DVB-S2), andDVB-S2 Extensions (DV13-S2X). In some examples, modcod schemes may belimited to a particular set of modcod schemes defined by such astandard, while in other examples, modcod schemes may not be limited todefined modcod schemes of any predetermined standard and may becustomized for a satellite system.

A suitable modcod scheme may be selected by a modcod selector 162 andmay be applied by modulator 160. Different modcod schemes may be used atdifferent times depending on conditions (e.g. weather conditions,interference, noise, etc.). FIG. 2C shows an example in which a feedbacksignal 164 is sent from subscriber terminal 166 to modcod selector 162of gateway 105. For example, subscriber terminal 166 may send feedbacksignal 164 via a return path using satellite 100, or in some othermanner. Feedback signal 164 in this example includes an indication ofsignal quality for data received by subscriber terminal 166 fromsatellite 100. In one embodiment a modem 166 that demodulates anddecodes incoming data from user beam 142_1 includes signal processing tomeasure SNR unit 168 that provides an indication of signal quality inthis example.

SNR detection unit 168 may provide an SNR value, a channel-to-noiseratio (CNR), signal to interference ratio (SIR), carrier to interferenceratio (CIR), carrier to noise plus interference ratio (CNIR), or othersuitable indicator of signal quality. While the term “SNR detectionunit” is used here, it will be understood that any suitable metric maybe used to indicate the quality of a received signal. The SNR detectionunit 168 provides signal quality data to ACM unit 170 which generates anindication of signal quality, feedback signal 164, which it sends tomodcod selector 162. Modcod selector 162 selects a suitable modcodscheme according to feedback signal 164, based on the indication ofsignal quality obtained from SNR detection unit 168. For example, whereSNR detection unit 168 shows that received data has low quality (e.g.low SNR) then modcod selector 162 may select a modcod scheme accordingly(e.g. high level of error protection and relatively low data rate).Modulator 160 then applies the selected modcod scheme to data sent tosubscriber terminal 166, which in this case is sent via feeder beam 150,to satellite 100, and via spot beam 142_1 to subscriber terminal 166.

FIG. 3 shows an alternative approach to using modcod schemes forsatellite communication. Unlike the example of FIG. 2C, satellite 300includes a demodulator 302 to demodulate incoming data (e.g. from afeeder beam 304), a switch 306 (which may also be referred to as aswitching network, or router) to direct incoming data to an appropriateoutput, and a modulator 308 to modulate data received from switch 306for sending (e.g. as a user link 310). Satellite 300 also includes a SNRdetection unit 312 connected to demodulator 302. Demodulator 302demodulates an incoming signal received via feeder beam 304 from gateway314. This signal is modulated by modulator 316 in gateway 314 using amodcod scheme selected by modcod selector 318 (e.g. an appropriatemodcod scheme defined by a standard such as DVB-S2X). Modcod selector318 receives a feedback signal 320 from ACM unit 313 in satellite 300(e.g. via a return path) that indicates signal quality of feeder beam304 when it is demodulated by demodulator 302. For example, demodulator302 may generate one or more indicators of signal quality whendemodulating and decoding incoming data and SNR detection unit 312 mayuse signal processing or demodulating and decoding information togenerate an indicator of signal quality, such as a bit error rate or anSNR value.

Switch 306 routes demodulated digital data to an appropriate destinationin satellite 300 (described in more detail below). Prior to being sentfrom satellite 300 to subscriber terminal 322, digital data is encodedand modulated by modulator 308 (e.g. using a suitable modcod schemeaccording to a standard, such as DVB-S2X). A modcod scheme used bymodulator 308 may be different from a modcod scheme used by modulator316 and demodulator 302. Thus, a first modcod scheme may be used forfeeder beam 304 (an input modcod scheme) while a second modcod scheme(an output modcod scheme) may be used for user link 310. A given portionof data that is sent from gateway 314 to subscriber unit 322 ismodulated and demodulated twice in this arrangement, with differentmodulation schemes applied for the first (gateway-to-satellite) portion,and the second (satellite-to-subscriber terminal) portion.

Using different modcod schemes in this manner may provide severaladvantages including more efficient use of available bandwidth. Forexample, where a single modcod scheme is used between a gateway and asubscriber terminal as shown in FIG. 2C, the modcod scheme may depend onthe weaker link between the satellite and subscriber terminal and thismay leave unused capacity on the stronger link between the gateway andsatellite (i.e. feeder beam could operate at higher data rate butencoding and modulation are limited by user link). Selection ofdifferent modcod schemes for different links may allow each modcodscheme to be optimized for conditions of the link for which it isselected.

FIG. 3 shows an SNR detection unit 324 coupled to demodulator 326 insubscriber unit 322. SNR detection unit 324 detects SNR or other measureof signal quality for user beam 310 at the location of 322 according todemodulation and decoding performed by decoder 326. ACM unit 328 thenprovides this signal quality information in feedback signal 329 tomodcod selection unit 318 of gateway 314.

In some cases, a feedback signal may be provided from a subscriberterminal to a satellite so that the selection of a suitable outputmodcod scheme for a user beam may be directly made on the satellite,without any involvement by a gateway. However, this may require someadditional hardware on a satellite. Furthermore, having completelyindependent selection of incoming and outgoing modcod schemes on asatellite may allow scenarios where incoming data arrives at a satellitefaster than it can be sent because an incoming modcod scheme may have ahigh encoding rate and an outgoing modcod scheme, or schemes, may havelow rates. Buffers may be required for such scenarios, which may addcost and complexity.

FIG. 3 shows both feedback signals 320 and 329 sent to modcod selectionunit 318 of gateway 314. Thus, modcod selection unit 318 receivesseparate indicators of quality for feeder beam 304 and user beam 310.Accordingly, modcod selection unit 318 may coordinate selection ofappropriate modcod schemes for both legs (i.e. an appropriate modcodscheme for first leg from gateway 314 to satellite 300 and anappropriate modcod scheme for second leg from satellite 300 tosubscriber terminal 322).

According to an example, modcod schemes for both legs are selected in acoordinated manner that ensures that outgoing data can be sent fromsatellite 300 faster than it arrives, thereby obviating the need forlarge buffers or complex data management schemes. Incoming modcodschemes and outgoing modcod schemes are linked according to theirencoding rates to ensure that data does not arrive at satellite 300faster than it can be sent onwards to subscriber terminals. Incomingmodcod schemes and outgoing modcod schemes may be linked in apredetermined arrangement. For example, a table known by the gatewaymodem select unit 318 and the satellite modulator 308 may tabulaterelationships between incoming modcod schemes and outgoing modcodschemes. Modcod selection unit 318 may select a pair of modcod schemes(incoming modcod scheme and outgoing modcod scheme) from such a table.Modulator 316 then applies the input modcod scheme to data sent overfeeder beam 304. For example, where feeder beam 304 is coupled to noutput channels or carriers (which may go to n or fewer feeder beams),an outgoing modcod scheme or schemes may be chosen for n encoders thatprovide a collective encoding rate more than an encoding rate of anincoming modcod scheme. For example, individual outgoing encoding ratemay be greater than 1/n times the input encoding rate.

A modcod scheme for user link 310 may be selected by satellite 100 inresponse to input from gateway 314 so that an input modcod scheme and anoutput modcod scheme are appropriately paired. According to an example,a satellite uses a lookup table to determine from the input modcodscheme which output modcod scheme to select as an output modcod scheme.The lookup table may be combined with other tables used by a switch toroute data, and may contain entries similar to entries used by modcodselector 318 to select an input modcod scheme and an output modcodscheme in a coordinated manner.

FIG. 4 shows an example of a satellite 400 that includes a demodulator402 for demodulating and decoding a signal of feeder beam 404 accordingto an input modcod scheme, a switch 406 (which may also be referred toas a switching network, or router) to direct incoming data to anappropriate output, and a modulator 408 to modulate data received fromswitch 406 for sending (e.g. as a user link 410). Satellite 400 alsoincludes an SNR detection unit 412 connected to demodulator 402 and anACM unit 413. An output modcod scheme selector 414 is coupled tomodulator 408 to select a modcod scheme to be used by modulator 408 toencode and modulate data sent over user link 410. Output modcod schemeselector 414 is also coupled to demodulator 402 to receive an indicatorfrom demodulator 402 as to what input modcod scheme demodulator 402 isusing (i.e. which modcod scheme is currently in use for data receivedover feeder beam 404). Output modcod scheme selector 414 is also coupledto a lookup table, LUT 416, which indicates a correspondence betweeninput modcod schemes and output modcod schemes. Modcod selector 414 isconfigured to select an output modcod scheme for output modulator 408based on the input modcod scheme according to the relationship betweeninput modcod schemes and output modcod schemes listed in LUT 416 (i.e.finding the entry for the current input modcod scheme and reading theoutput modcod scheme for that entry). Thus, in this example, no separatecommand is provided from a gateway to indicate a modcod scheme to beused by modulator 408, the output modcod scheme is simply selected basedon the input modcod scheme according to a lookup table. LUT 416 may beupdated as needed from the ground and generally reflects input modcodschemes linked to output modcod schemes with encoding rates that ensurethat data can be sent faster than it is received.

FIG. 5 shows a simplified schematic of a regenerative payload onsatellite 500 that includes on-board processing. Satellite 500's payloadincludes an RF front-end 502 “RF front-end, DoCON” that receives nGateway uplinks and includes down-converters to convert frequencies ofreceived RF signals. Outputs from RF front-end 502 are provided to OBP(On-Board Processor) 504, which performs demodulation, decoding,routing, encoding, and modulation. Thus, OBP 504 receives RF inputs andgenerates RF outputs, with intermediate steps that convert inputs todigital data and route the digital data in packets, to appropriateoutputs. Outputs of OBP 504 are provided to RF back-end 506 “UpCON, RFback-end, HPAs” which includes up-converters to convert frequencies ofRF signals from OBP 504 and High-Power Amplifiers (HPAs) to amplify RFsignals for transmission. Outputs from RF back-end 506 are provided to Muser downlink beams (e.g. spot beams). A power distribution unit 508receives a 100 volt direct current power input and distributeselectrical power to components including RF front-end 502, OBP 504, andRF back-end 506. An OBP controller 510 is coupled to OBP 504 andcontrols OBP 504 including routing of signals through OBP 504. Forexample, OBP controller may use one or more tables to manage routing ofdata and to manage modcod selection. OBP controller 510 is incommunication with a ground control center through a telemetry,tracking, and command (TT&C) system, which may provide routing and othercommands that are used by OBP controller 510 to operate OBP 504. A clockgeneration/distribution unit 512 receives an input from an MRO (MasterReference Oscillator) and distributes clock signals to componentsincluding RF front-end 502, OBP 504, and RF back-end 506. Use of an OBPto demodulate, route, and modulate signals provides a high degree offlexibility in how communications are handled and provides severalbenefits.

FIG. 6 shows an example of a satellite 600 that includes an on-boardprocessor OBP 602 and a return payload 604 (additional components suchas upconverters, amplifiers, etc. are not shown for clarity). Returnpayload 604 includes hardware for providing return path data fromsubscriber terminals to gateways, where return path data includes dataused for ACM purposes, for example, an indication of signal quality.Satellite 600 is shown in communication with two gateways, gateway A andgateway B. A feeder uplink 606 from Gateway A is provided to ananalog-to-digital converter, ADC 608, in OBP 602. Digital output fromADC 608 includes data for transmission to multiple subscriber terminalsvia multiple output carriers, which may use multiple spot beams. In thisexample, digital output from ADC 608 corresponds to four output carriersor channels and the digital data is sent to four demodulators 611-614accordingly (e.g. using one or more demultiplexers). Demodulators611-614 each perform demodulation and decoding of data using an inputmodcod scheme (i.e. using the modcod scheme selected and used by gatewayA). Demodulated output from demodulators 611-614 is provided to inputports of switch 620. Switch 620 then directs digital input fromdemodulators 611-614 to appropriate output ports. Digital data may berouted in any suitable manner between input ports and output ports ofswitch 620, e.g. using header information in packets, using time slotindicators, or otherwise. While FIG. 6 shows equal numbers of inputports and output ports, in other examples, these numbers may not beequal (e.g. there may be more output ports than input ports). Data isoutput via output ports to modulators 621-628, which perform encodingand modulation according to one or more output modcod schemes and thenpass encoded modulated data to digital-to-analog converters (DACs) thatprovide RF outputs, which are sent to subscriber terminals. For example,data from ADC 608 that is provided to demodulator 613 is routed tomodulator 621 which encodes and modulates the before providing it to DAC630 to send as a user beam 1 to subscriber terminal 632. Outputs fromother ports of switch 620 are sent to other modulators and DACs and areprovided as user beams 2-8 as shown (e.g. via the same, or differentspot beams, to additional subscriber terminals that are not shown inthis illustration).

Feedback to gateway A for ACM is generated by both satellite 600 andsubscriber terminal 632. ACM data is sent via return path 634 fromsubscriber terminal 632, e.g. subscriber terminal 632 sends an indicatorof signal quality for user beam 1, such as an SNR value. Return path 634is received by return payload 604 of satellite 600 where the returnsignal is amplified by amplifier 636 and its frequency is upconverted byupconverter 638 and provided to a multiplexer, MUX 640. Demodulator 611also provides an indicator of signal quality for feeder uplink 606,which is provided to return payload 604 via pathway 642. Because datafrom feeder uplink 606 is provided to multiple demodulators, signalquality data can be provided by any of one of the modulators, or bymultiple demodulators. For simplicity, and to save weight and power, asingle demodulator (demodulator 611) receiving data from feeder uplink606 is used to provide signal quality data (e.g. SNR) in this example.In other examples, a different demodulator, or demodulators may be usedto provide signal quality data. A signal from pathway 642 is upconvertedby upconverter 644 and is provided to MUX 640. MUX 640 combines thesignals representing signal quality of feeder uplink 606 and signalquality of user beam 1 to provide an output that is amplified byamplifier 646, combined with other return pathway data by MUX 648 andsent to gateway A via return downlink 650. Thus, gateway A receivesseparate feedback for each leg of data transmission between gateway Aand subscriber terminal (feeder uplink 606 to satellite 600 and userbeam 1 from satellite 600).

FIG. 6 shows a cloud 660 along the pathway of feeder beam 662 betweengateway B and satellite 600. Cloud cover or other factors may cause oneor more feeder beams to be degraded. Redundancy may be provided toreduce the risk of a gateway being unusable (e.g. redundant gateways maybe provided). However, redundancy may be costly. Using switch 620,ensures that data may be provided to all user beams even when a gatewaybecomes unusable. For example, if gateway B is unusable, thendemodulators 615-618 do not receive data and thus, switch 620 has noinput on four of eight input ports. However, data that would have beensent via gateway B may be directed to gateway A (e.g. via ground networksuch as a fiber optic network) and may be combined with other data andsent to satellite 600 where switch 620 routes data appropriately tomaintain service. For example, where feeder beam 662 was coupled to userbeams 1-8 and then stopped functioning, this data may be routed throughgateway A (which was idle) to satellite 600 and may be routed by switch620 to modulators 625-628, through DACs to user beams 1-8. Thus, inputsand outputs of switch 620 are not necessarily linked in a one-to-onerelationship. Multiple data channels are combined in feeder beams andmay be demultiplexed (e.g. using time division demultiplexing, frequencydivision demultiplexing, or otherwise) into individual channels in aflexible manner that allows the number of channels serviced by a givenfeeder beam to increase to compensate for degradation or loss of anothergateway.

FIG. 7 shows an example of how a processor 700 may route input channelsto output channels (output carriers). Input channels A-F are received ona feeder uplink as six channels of 500 MHz within a 3 GHz band (V-band).Input channels A-F are digital input channels in this example (ananalog-to-digital converter, not shown in FIG. 7, may convert analoginput from an antenna to digital output). These channels aredemultiplexed by 1:6 demultiplexer 702 (e.g. frequency divisiondemultiplexing), which provides channels A-F separately to demodulators704 (“DVB-S2X Demodulator/PLHeader Decoder”), which demodulate anddecode data according to modcod schemes of the DVB-S2X standard. Eachchannel, A-F is demodulated and decoded by a corresponding demodulatorand different modcod schemes may be used for different channels. Outputsfrom demodulators 704 are provided as inputs to input ports of switch706 which then routes demodulated and decoded data from input ports tooutput ports. One input port may provide data that is distributed to oneor more output ports. In the example of FIG. 7, input data from sixinput ports is distributed to twelve output ports, with data from anindividual input port distributed to two output ports. In otherexamples, data from an input port may fan out to more than two outputports (e.g. twelve output ports). Digital data from output ports ofswitch 706 is provided to corresponding modulators 708, which applyDVB-S2X modulation to provide ACM (“ACM adaptation DVB-S2X Modulator”)on each output channel. Output channels are then provided to multiplexer710 allowing multiple modulated carriers to be routed to one user beamwhich provides the twelve output channels A1-F2 for sending in spotbeams. Output channels are numbered according to their correspondinginput channels. Thus, output channels A1 and A2 correspond to inputchannel A, output channels B1 and B2 correspond to input channel B, andso on. While processor 700 manages six input channels A-F in thisexample, additional input channels G-L (e.g. from another feeder beam)may be similarly managed by another processor to provide another twelveoutput channels. Additional input channels may be similarly handled byadditional processors. Such processors may be interconnected to allowrouting of data between processors. Switches of individual processors(such as switch 706 of processor 700) may be linked together to form aswitching fabric that may allow data from an input port of any linkedswitch to be sent to an output port of any linked switch. For example,input channel G may be demodulated and decoded (not shown in FIG. 7) andprovided to an input port of a switch that is linked to switch 706.Corresponding outputs (e.g. G1 and G2) may be routed to switch 706 andto modulators 780 and provided as outputs of processor 700.

FIG. 8 shows an example of how input from a gateway (GW1) may be handledusing on-board processing. An analog-to-digital converter, ADC 804,receives input from GW1 as a 3000 MHz RF input, consisting of 6 carriersof 500 MHz, which is demultiplexed by 1:6 demultiplexer 806 into sixseparate carriers that are separately demodulated and decoded bydemodulators 808 (“DVB-S2X demodulator/PLHeader Decoder”) according to amodcod scheme or schemes used to encode and modulate data at GW1. Forexample, a spectrum efficiency of about 4.5 bits/Hz may provide a datarate of about 2 Gbps, modulated at 476 MSymb/s. Outputs of demodulators808 are provided to input ports of switch 810 a, which directs inputdata to twelve output ports as before (one-to-two fan out). Routing maybe performed according to one or more tables, which may also be used formodcod selection. Outputs are encoded by encoders 812, which maygenerate new physical layer (“PL”) headers and modulate according tomodcod schemes defined by DVB-S2X standard based on modulationcorrelation tables. For example, a data rate of about 2.3 bits/Hz mayprovide a data rate of about 1 Gbps, or about half of the data rate ofdemodulators 808. Outputs of encoders 812 are provided to outputmultiplexers 814 a-d which allow multiple carriers to be routed to asingle beam and then converted by digital-to-analog converters (“DAC”)into analog outputs, beams 1-12, which may be spot beams from asatellite.

Switch 810 a is connected to a High Speed Serial Link (HSSL) 815 whichconnects switch 810 a and switch 810 b, and may connect one or moreother switches (not shown). A bidirectional serializer/deserializer(SerDes) link on a HSSL may provide a data speed of about 12.5 Gbps.Thus, data from an input port of one switch such as switch 810 a may berouted to an output port of another switch such as switch 810 b. Where aparticular switch is generally associated with a particular gateway andthat gateway is not in operation (e.g. because of weather, did not getfunding, or other condition) then data may be rerouted through othergateways to inputs of other switches and then, through a HSSL, tooutputs of the particular switch and on to beams associated with theparticular switch in what may be considered “diversity switching” andmay also provide gateway roll out flexibility. In this way, spot beamsmay be maintained after the gateway normally associated with those spotbeams fails (though this may be at a lower data rate). Switches combinedin this manner form a switching fabric that may operate as a singleswitch so that data from any input port can be routed to any outputport.

One or more tables may be used to manage operation of OBPs in a simplelow-cost manner. For example, where an input channel fans out to providemultiple output channels, the relationships between inputs and outputsmay be established by one or more tables. In one embodiment, FEC frameswithin a modcod block that is received at an input port of an OBP may berouted to output ports according to a table. FIG. 9A shows an example ofhow a modcod block 900 is made up of multiple Forward Error Correction(FEC) frames (FEC1-FEC80). For example, a modcod block may consist of 80FEC frames as shown. A modcod block is a minimum unit of a modcod systemso that all data of a modcod block is subject to the same modcod scheme.Different modcod blocks may be subject to different modcod schemes (i.e.modcod scheme may change from modcod block to modcod block). Modcodblock 900 may be a portion of data that is received on a given inputport and is demodulated and decoded according to a modcod scheme. FECdecoding may be performed on a frame-by-frame basis with each FEC frameincluding user data and FEC data.

FIG. 9B shows an example of a table that indicates how FEC frames ofmodcod block may be routed to output ports. In this example, data of amodcod block that is received on a given input port (e.g. input port 1)is distributed to four output ports (O/P 1-O/P 4) as shown. This may beconsidered as a form of time division demultiplexing. While data isdistributed evenly in this example, with each output port receiving 20FEC frames of an 80 frame modcod block, in other examples, data may beunevenly distributed with some output ports getting more data thanothers. The distribution of frames to output ports may continue overmany modcod blocks, for example, until the table is updated for somereason. The table may be updated by a network control center assubscriber needs change.

In some cases, two or more carriers are configured per output port. Atable may be used to indicate which data is provided to carriers of anoutput port. This table may be separate from a table assigning data tooutput ports (e.g. as shown in FIG. 9B) or may be combined as a tablethat shows both the output ports and the carriers.

FIG. 9C shows an example of a table that shows both assignment of FECframes to output ports and FEC frames to carriers of each port. In thisexample, a modcod block of 80 FEC frames is distributed to two outputports, O/P 1 and O/P 2, each having two carriers, A and B. FEC framesare distributed evenly between these four carriers in this example. Inother examples, FEC frames may be unevenly distributed between outputports and/or between carriers.

FIG. 10 shows an example of a modcod table that includes a column withinput modcod schemes and a column with corresponding output modcodschemes. For any given input modcod scheme a corresponding output modcodscheme is listed. Thus, for example, input modcod scheme 2 is linkedwith corresponding output modcod scheme 12. Where data is received thatis modulated and encoded according to input modcod scheme 2, this tablemay be consulted to identify modcod scheme 12 as the correspondingoutput modcod scheme. Output modulators may then be configuredaccordingly to encode and modulate data using modcod scheme 12.

According to one aspect of the present disclosure, a satellite includesan input demodulator configured to apply an input modulation and coding(modcod) scheme; an output modulator configured to apply an outputmodcod scheme; and an output modcod scheme selector configured to selectan output modcod scheme for the output modulator based on the inputmodcod scheme according a predetermined relationship between inputmodcod schemes and output modcod schemes. An input modulation and codingscheme (modcod scheme) may be automatically detected by an inputdemodulator, e.g. by detecting a header of an FEC frame.

Optionally, the satellite may include a lookup table that specifies thepredetermined relationship between a plurality of input modcod schemesand a plurality of output modcod schemes, each input modcod schemelinked to a respective output modcod scheme.

Optionally, the plurality of input modcod schemes and the plurality ofoutput modcod schemes are Digital Video Broadcasting-Second generationExtended (DVB-S2X) modcod schemes.

Optionally, the satellite may include a channel lookup table containingentries allocating an input received by the satellite from a gateway toa plurality of output channels.

Optionally, the plurality of output channels consists of n outputchannels, the output modcod scheme selector is configured to select theoutput modcod scheme for n output modcod units associated with the noutput channels based on the input modcod scheme such that the outputmodcod scheme has an output data rate that is greater than 1/n times adata rate of the input modcod scheme, or individual output data rates ofthe n output channels have a collective output data rate that is greaterthan or equal to the data rate of the input modcod scheme.

Optionally, the satellite may include a frame lookup table, the framelookup table configured to allocate the input received by the satellitefrom the gateway among the plurality of output channels with differentframes allocated to different output channels.

Optionally, the frame lookup table has entries for modcod blocks, amodcod block being a minimum unit for applying modcod schemes, andwherein the frame lookup table allocates frames of a given modcod blockin a pattern indicated by the frame lookup table.

Optionally, the satellite includes a return payload connected to theinput demodulator to receive an indication of input signal quality fordata demodulated by the input demodulator and to return the indicationof input signal quality to a sender of input data.

Optionally, the return payload is further configured to receive anindication of output signal quality for data sent using the outputmodcod scheme and to relay the indication of output signal quality tothe sender of input data.

Optionally, a switch is interposed between an input demodulator and theoutput modulator, the switch configurable to couple the inputdemodulator with any output modulator in the satellite.

According to one aspect of the present disclosure, a satellite systemincludes a gateway that includes a gateway modulator configured to applya first modulation and coding (modcod) scheme to forward link data; asatellite that includes: a demodulator configured to demodulate receivedforward link data using the first modcod scheme; a first signal qualitydetector (e.g. a Signal to Noise Ratio (SNR) detector, or other detectorof signal quality) configured to identify a first signal qualityindicator (e.g. SNR) for the received forward link data; a returnpayload connected to the first signal quality detector (e.g. SNRdetector) to send the first signal quality indicator (e.g. SNR) for thereceived forward link data to the gateway; a modcod scheme selectorconfigured to select a second modcod scheme according to the firstmodcod scheme; a satellite modulator configured to modulate the forwardlink data using the second modcod scheme; a transmitter configured totransmit the forward link data modulated by the satellite modulator; anda subscriber terminal configured to receive the forward link datatransmitted by the transmitter, the subscriber terminal including asecond signal quality detector (e.g. SNR detector) configured toidentify a second signal quality indicator (e.g. SNR) for forward linkdata received by the sub scriber terminal.

Optionally, the subscriber terminal includes a transmitter configured totransmit the second SNR to the gateway.

Optionally, the gateway is configured to select the first modcod schemeaccording to the second signal quality indicator (e.g. second SNR).

Optionally, the modcod scheme selector includes a modcod lookup tablethat defines a predetermined relationship between the first modcodscheme and the second modcod scheme.

Optionally, the satellite further includes a carrier mapping table and aswitch that is configured to allocate received forward link data to aplurality of output carriers according to the carrier mapping table.

Optionally, the switch is further configured to allocate the receivedforward link data to a plurality of output beams, each output beamincluding two or more output carriers.

Optionally, the switch is further configured to allocate the receivedforward link data to the plurality of output carriers according to aframe allocation table in the satellite that allocates frames of amodcod block to output carriers.

According to one aspect of the present disclosure, a satellite includesa plurality of processors including at least a first processor and asecond processor, each processor having a plurality of input ports and aplurality of output ports; a data link between the plurality ofprocessors to permit data flow between at least the first processor andthe second processor; and a routing table that indicates connection ofinput ports and output ports of the plurality of processors, including aconnection between an input port of the first processor and an outputport of the second processor.

Optionally, each processor includes a plurality of input demodulatorsconnected to the plurality of input ports and a plurality of outputmodulators connected to the plurality of output ports, the satellitefurther comprising a modulation and coding (modcod) table that indicatesa predetermined relationship between input modcod schemes applied by theplurality of input demodulators and output modcod schemes applied by theplurality of output modulators.

Optionally, a modcod block is a minimum unit of modulation and encodingof the input modcod schemes applied by the plurality of inputdemodulators and the routing table includes mapping of frames of amodcod block received at the input port of the first processor to one ormore output ports including the output port of the second processor.

For purposes of this document, it should be noted that the dimensions ofthe various features depicted in the figures may not necessarily bedrawn to scale.

For purposes of this document, reference in the specification to “anembodiment,” “one embodiment,” “some embodiments,” or “anotherembodiment” may be used to describe different embodiments or the sameembodiment.

For purposes of this document, a connection may be a direct connectionor an indirect connection (e.g., via one or more other parts). In somecases, when an element is referred to as being connected or coupled toanother element, the element may be directly connected to the otherelement or indirectly connected to the other element via interveningelements. When an element is referred to as being directly connected toanother element, then there are no intervening elements between theelement and the other element. Two devices are “in communication” ifthey are directly or indirectly connected so that they can communicateelectronic signals between them.

For purposes of this document, the term “based on” may be read as “basedat least in part on.”

For purposes of this document, without additional context, use ofnumerical terms such as a “first” object, a “second” object, and a“third” object may not imply an ordering of objects, but may instead beused for identification purposes to identify different objects.

The foregoing detailed description has been presented for purposes ofillustration and description. It is not intended to be exhaustive or tolimit the subject matter claimed herein to the precise form(s)disclosed. Many modifications and variations are possible in light ofthe above teachings. The described embodiments were chosen in order tobest explain the principles of the disclosed technology and itspractical application to thereby enable others skilled in the art tobest utilize the technology in various embodiments and with variousmodifications as are suited to the particular use contemplated. It isintended that the scope of be defined by the claims appended hereto.

What is claimed is:
 1. A satellite, comprising: an input demodulatorconfigured to apply an input modulation and coding (modcod) scheme; anoutput modulator configured to apply an output modcod scheme; and anoutput modcod scheme selector configured to select an output modcodscheme for the output modulator based on the input modcod schemeaccording a predetermined relationship between input modcod schemes andoutput modcod schemes.
 2. The satellite of claim 1 further comprising alookup table that specifies the predetermined relationship between aplurality of input modcod schemes and a plurality of output modcodschemes, each input modcod scheme linked to a respective output modcodscheme.
 3. The satellite of claim 2 wherein the plurality of inputmodcod schemes and the plurality of output modcod schemes are DigitalVideo Broadcasting-Second generation Extended (DVB-S2X) modcod schemes.4. The satellite of claim 1 further comprising a channel lookup tablecontaining entries allocating an input received by the satellite from agateway to a plurality of output channels.
 5. The satellite of claim 4wherein the plurality of output channels consists of n output channels,the output modcod scheme selector is configured to select the outputmodcod scheme for n output modcod units associated with the n outputchannels based on the input modcod scheme such that the output modcodscheme has an output data rate that is equal to or greater than the datarate of the input modcod scheme in aggregate or as allocated for outputn.
 6. The satellite of claim 4 further comprising a frame lookup table,the frame lookup table configured to allocate the input received by thesatellite from the gateway among the plurality of output channels withdifferent frames allocated to different output channels.
 7. Thesatellite of claim 6 wherein the frame lookup table has entries formodcod blocks, a modcod block being a minimum unit for applying modcodschemes, and wherein the frame lookup table allocates frames of a givenmodcod block in a pattern indicated by the frame lookup table.
 8. Thesatellite of claim 1 further comprising a return payload connected tothe input demodulator to receive an indication of input signal qualityfor data demodulated by the input demodulator and to return theindication of input signal quality to a sender of input data.
 9. Thesatellite of claim 8 wherein the return payload is further configured toreceive an indication of output signal quality, from a device externalto the satellite, for data sent using the output modcod scheme and torelay the indication of output signal quality to the sender of inputdata.
 10. The satellite of claim 1 further comprising a switchinterposed between an input demodulator and the output modulator, theswitch configurable to couple the input demodulator with any outputmodulator in the satellite.
 11. A satellite system comprising: a gatewaythat includes a gateway modulator configured to apply a first modulationand coding (modcod) scheme to forward link data and a first modcodscheme selector relating a second modcod scheme to the first modcodscheme; a satellite that includes: a demodulator configured todemodulate received forward link data using the first modcod scheme; afirst signal quality detector configured to identify a first signalquality indicator for the received forward link data; a return payloadconnected to the first signal quality detector to send the first signalquality indicator for the received forward link data to the gateway; asecond modcod scheme selector configured to select the second modcodscheme according to the first modcod scheme; a satellite modulatorconfigured to modulate the forward link data using the second modcodscheme; a transmitter configured to transmit the forward link datamodulated by the satellite modulator; and a subscriber terminalconfigured to receive the forward link data transmitted by thetransmitter, the subscriber terminal including a second signal qualitydetector configured to identify a second signal quality indicator forforward link data received by the subscriber terminal.
 12. The satellitesystem of claim 11 wherein the subscriber terminal includes atransmitter configured to transmit the second signal quality indicatorto the gateway.
 13. The satellite system of claim 11 wherein the gatewayis configured to select the first modcod scheme according to a functionof the first and second signal quality indicators.
 14. The satellitesystem of claim 11 wherein the first and second modcod scheme selectorsinclude a modcod lookup table that defines a predetermined relationshipbetween the first modcod scheme and the second modcod scheme.
 15. Thesatellite system of claim 11 wherein the satellite further includes acarrier mapping table and a switch that is configured to allocatereceived forward link data to a plurality of output carriers accordingto the carrier mapping table.
 16. The satellite system of claim 15wherein the switch is further configured to allocate the receivedforward link data to a plurality of output beams, each output beamincluding one or more output carriers.
 17. The satellite system of claim15 wherein the switch is further configured to allocate the receivedforward link data to the plurality of output carriers according to aframe allocation table in the satellite that allocates frames of amodcod block to output carriers.
 18. A satellite, comprising: aplurality of processors including at least a first processor and asecond processor, each processor having a plurality of input ports and aplurality of output ports; a data link between the plurality ofprocessors to permit data flow between at least the first processor andthe second processor; and a routing table that indicates connection ofinput ports and output ports of the plurality of processors, including aconnection between an input port of the first processor and an outputport of the second processor.
 19. The satellite of claim 18 wherein eachprocessor includes a plurality of input demodulators connected to theplurality of input ports and a plurality of output modulators connectedto the plurality of output ports, the satellite further comprising amodulation and coding (modcod) table that indicates a predeterminedrelationship between input modcod schemes applied by the plurality ofinput demodulators and output modcod schemes applied by the plurality ofoutput modulators.
 20. The satellite of claim 19 wherein a modcod blockis a minimum unit of modulation and encoding of the input modcod schemesapplied by the plurality of input demodulators and wherein the routingtable includes mapping of frames of a modcod block received at the inputport of the first processor to one or more output ports including theoutput port of the second processor.